Wakeup radio (WUR) packet preamble design

ABSTRACT

A first communication device generates a first portion and a second portion of a wakeup radio (WUR) wakeup packet. The first portion of the WUR wakeup packet corresponds to a wireless local area network (WLAN) legacy preamble, and spans a first frequency bandwidth. The second portion of the WUR wakeup packet spans a second bandwidth that is less than the first bandwidth, and is configured to cause a WUR of a second communication device to cause a WLAN network interface device of the second communication device to transition from a low power state to the active state. Generating the second portion of the WUR wakeup packet includes i) generating a sync portion having a plurality of sync symbols, and ii) generating a wakeup packet body. The first communication device transmits the WUR wakeup packet.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/652,146, entitled “Wake-up Radio (WUR) PreambleFormat Design,” filed on Apr. 3, 2018, the disclosure of which is herebyexpressly incorporated herein by reference in its entirety.

FIELD OF TECHNOLOGY

The present disclosure relates generally to wireless communicationsystems, and more particularly to formats of packets for communicationsystems employing wakeup radios (WURs).

BACKGROUND

Wireless local area networks (WLANs) have evolved rapidly over the pastdecade, and development of WLAN standards such as the Institute forElectrical and Electronics Engineers (IEEE) 802.11 Standard family hasimproved single-user peak data throughput. For example, the IEEE 802.11bStandard specifies a single-user peak throughput of 11 megabits persecond (Mbps), the IEEE 802.11a and 802.11g Standards specify asingle-user peak throughput of 54 Mbps, the IEEE 802.11n Standardspecifies a single-user peak throughput of 600 Mbps, and the IEEE802.11ac Standard specifies a single-user peak throughput in thegigabits per second (Gbps) range. Future standards promise to provideeven greater throughput, such as throughputs in the tens of Gbps range.

Some WLANs include low cost wireless devices, such as wireless sensors,that do not require high data rates. To reduce operating costs, it maybe useful for such wireless devices to be battery operated or otherwisepower constrained. Power saving techniques for reducing powerconsumption are used with such power-constrained wireless devices. Forexample, a WLAN network interface of a power-constrained wireless deviceis put into to a low power state (e.g., a sleep state) for periods oftime in order to decrease power consumption of the wireless device. Whenthe wireless device is ready to transmit data to an access point, theWLAN network interface is transitioned to an active state so that thedata can be transmitted. After the WLAN network interface transmits thedata, the WLAN network interface transitions back to the low powerstate.

A WLAN network interface of a power-constrained wireless device may“wake up” periodically to listen for transmissions from the access pointto determine whether the access point has data to transmit to thewireless device. However, such periodic “wake ups” by the WLAN networkinterface consume power even when the access point has no data totransmit to the wireless device. Therefore, to further reduce powerconsumption, some wireless devices employ a low power wakeup radio(LP-WUR) that consumes much less power as compared to the WLAN networkinterface. For example, the LP-WUR does not include any transmittercircuitry and may be capable of only receiving very low data ratetransmissions. When the access point is ready to transmit data to thewireless device, the access point transmits a wakeup radio (WUR) wakeuppacket (referred to herein simply as a “wakeup packet”) addressed to thewireless device. In response to receiving the wakeup packet anddetermining that the wakeup packet is addressed to the wireless device,the LP-WUR wakes up the WLAN network interface so that the WLAN networkinterface is ready to receive data from the access point.

SUMMARY

In an embodiment, a method is performed by a first communication deviceand is for transmitting a wakeup packet configured to cause a wakeupradio of a second communication device to cause a wireless local areanetwork (WLAN) network interface device of the second communicationdevice to transition from a low power state to an active state. Themethod includes: generating, at the first communication device, a firstportion of the wakeup packet, wherein the first portion of the wakeuppacket corresponds to a WLAN legacy preamble of the wakeup packet, andwherein the first portion spans a first frequency bandwidth; generating,at the first communication device, a second portion of the wakeuppacket, wherein the second portion of the wakeup packet spans a secondbandwidth that is less than the first bandwidth, and wherein: the secondportion of the wakeup packet is configured to cause the wakeup radio ofthe second communication device to cause the WLAN network interfacedevice of the second communication device to transition from the lowpower state to the active state, generating the second portion of thewakeup packet includes i) generating a sync portion having a pluralityof sync symbols, and ii) generating a wakeup packet body. The methodalso includes transmitting, by the first communication device, thewakeup packet.

In another embodiment, an apparatus comprises: a network interfacedevice associated with a first communication device, wherein the networkinterface device comprises one or more integrated circuit (IC) devices.The one or more IC devices are configured to: generate a wireless localarea network (WLAN) legacy preamble of a wakeup packet, wherein thewakeup packet is configured to cause a wakeup radio of a secondcommunication device to cause a WLAN network interface device of thesecond communication device to transition from a low power state to anactive state. The one or more IC devices are also configured to:generate a first portion of a wakeup packet, wherein the first portionof the wakeup packet corresponds to a wireless local area network (WLAN)legacy preamble of the wakeup packet, and wherein the first portionspans a first frequency bandwidth. The one or more IC devices arefurther configured to: generate a second portion of the wakeup packet,wherein the second portion of the wakeup packet spans a second bandwidththat is less than the first bandwidth, and wherein: the second portionof the wakeup packet is configured to cause a wakeup radio of a secondcommunication device to cause a WLAN network interface device of thesecond communication device to transition from a low power state to anactive state, and generating the second portion of the wakeup packetincludes i) generating a sync portion having a plurality of syncsymbols, and ii) generating a wakeup packet body. Additionally, the oneor more IC devices are further configured to transmit the wakeup packet.

In yet another embodiment, a method is performed by a wakeup radio (WUR)of a communication device and is for processing a wakeup packetconfigured to cause the WUR of the communication device to cause awireless local area network (WLAN) network interface device of thecommunication device to transition from a low power state to an activestate. The wakeup packet includes i) a first portion having a WLANlegacy preamble that spans a first frequency bandwidth, and ii) a secondportion that follows in time the first portion and that spans a secondbandwidth narrower than the first bandwidth. The second portion includesi) a sync portion having a plurality of sync symbols, and ii) a wakeuppacket body. The method includes: calculating, at the WUR, one or morecorrelations corresponding to one or more sync symbols included in thesync portion; detecting, at the WUR, the sync portion of the wakeuppacket using the one or more correlations; determining, at the WUR, asymbol timing using the one or more correlations; and processing, at theWUR, the wakeup packet body based on the determined symbol timing.

In still another embodiment, an apparatus comprises: a wakeup radio WURassociated with a wireless local area network (WLAN) network interfacedevice. The WUR comprises one or more integrated circuit (IC) devicesconfigured to: process a wakeup packet. The wakeup packet includes i) afirst portion having a WLAN legacy preamble that spans a first frequencybandwidth, and ii) a second portion that follows in time the firstportion and that spans a second bandwidth narrower than the firstbandwidth. The second portion includes i) the sync portion having aplurality of sync symbols, and ii) a wakeup packet body. Processing thewakeup packet includes calculating one or more correlationscorresponding to one or more sync symbols included in the sync portion,detecting the sync portion of the wakeup packet using the one or morecorrelations, determining a symbol timing using the one or morecorrelations, and processing the wakeup packet body based on thedetermined symbol timing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of an example wireless local area network(WLAN) having a client station with a low power wakeup radio (LP-WUR),according to an embodiment.

FIG. 1B is a block diagram of an example wireless network interfacedevice of an access point included in the WLAN of FIG. 1A, according toan embodiment.

FIG. 1C is a block diagram of an example wireless network interfacedevice of the client station included in the WLAN of FIG. 1A, accordingto an embodiment.

FIG. 1D is a block diagram of an example LP-WUR in the WLAN of FIG. 1A,according to an embodiment.

FIG. 2 is a diagram of a wakeup packet, according to an embodiment.

FIG. 3A is a diagram of an example payload of the wakeup packet of FIG.2, according to an embodiment.

FIG. 3B is a diagram of another example payload of the wakeup packet ofFIG. 2, according to another embodiment.

FIG. 4 is a diagram of an example wakeup radio (WUR) sync portion of awakeup packet, according to another embodiment.

FIG. 5A is a diagram of an example WUR sync portion selection devicethat is included in one or more of the communication devices of FIGS.1A-C, according to an embodiment.

FIG. 5B is a diagram of another example WUR sync portion selectiondevice that is included in one or more of the communication devices ofFIGS. 1A-C, according to another embodiment.

FIG. 6 is a flow diagram of an example method for generating wakeuppackets, according to an embodiment.

FIG. 7 is a block diagram of an example WUR preamble detector, accordingto an embodiment.

FIG. 8 is a block diagram of another example WUR preamble detector,according to another embodiment.

FIG. 9 is a block diagram of another example WUR preamble detector,according to another embodiment.

FIG. 10 is a flow diagram of an example method for processing a wakeuppacket, according to an embodiment.

DETAILED DESCRIPTION

Techniques for generating and processing packets are described below inthe context of low power wakeup radios merely for explanatory purposes.In other embodiments, packet generation and processing techniques areutilized in other types of wireless communication systems such aspersonal area networks (PANs), mobile communication networks such ascellular networks, metropolitan area networks (MANs), satellitecommunication networks, etc., that use a narrower bandwidth than WLANs.

FIG. 1A is a block diagram of an example WLAN 110, according to anembodiment. The WLAN 110 includes an access point (AP) 114 thatcomprises a host processor 118 coupled to a wireless network interfacedevice 122. The wireless network interface device 122 is coupled to aplurality of antennas 126. Although three antennas 126 are illustratedin FIG. 1A, the AP 114 includes other suitable numbers (e.g., 1, 2, 4,5, etc.) of antennas 126 in other embodiments. As will be described inmore detail below, the wireless network interface device 122 isconfigured to generate and transmit a wakeup packet that can be decodedby low power wakeup radios (LP-WURs) in the WLAN 110.

The host processor 118 is configured to executed machine readableinstructions stored in a memory device (not shown), according to anembodiment. The host processor 118 is implemented on an integratedcircuit (IC), according to an embodiment. The wireless network interfacedevice 122 is implemented on one or more ICs. The host processor 118 isimplemented on one IC and the wireless network interface device 122 isimplemented on one or more other, different ICs, according to anembodiment. The host processor 118 is implemented on a first IC and thewireless network interface device 122 is implemented on at least thesame first IC and optionally on one or more second ICs, according to anembodiment.

The WLAN 110 also includes one or more client stations 134. Althoughthree client stations 134 are illustrated in FIG. 1A, the WLAN 110includes other suitable numbers (e.g., 1, 2, 4, 5, 6, etc.) of clientstations 134 in various embodiments. The client station 134-1 includes ahost processor 138 coupled to a wireless network interface device 142.The wireless network interface device 142 is coupled to one or moreantennas 146. Although three antennas 146 are illustrated in FIG. 1A,the client station 134-1 includes other suitable numbers (e.g., 1, 2, 4,5, etc.) of antennas 146 in other embodiments.

The wireless network interface device 142 is configured to go into a lowpower state in which the wireless network interface device 142 consumessignificantly less power as compared to an active state of the wirelessnetwork interface device 142. The wireless network interface device 142is capable of wirelessly receiving and transmitting via the one or moreantennas 146 while in the active state. In an embodiment, the wirelessnetwork interface device 142 is incapable of wirelessly receiving andtransmitting via the one or more antennas 146 while in the low powerstate.

The client station 134-1 also includes a LP-WUR 150 coupled to thewireless network interface device 142 and to at least one of theantennas 146. The LP-WUR 150 is configured to use very low power (e.g.,less than 100 microwatts or another suitable amount of power). TheLP-WUR 150 is configured to use significantly less power (e.g., lessthan 20%, less than 10%, less than 5%, less than 2%, less than 1%, etc)than the wireless network interface device 142 while the wirelessnetwork interface device 142 is in the active state, according to anembodiment.

The LP-WUR 150 is configured to receive and decode wakeup packetstransmitted by the AP 114 and received via one or more of the antennas146. The LP-WUR 150 is configured to determine whether a received wakeuppacket includes an address (e.g., a media access control (MAC) address,an association identifier (AID), or another suitable network address)corresponding to the client station 134-1, according to an embodiment.The LP-WUR 150 is configured to generate a wakeup signal in response todetermining that a received wakeup packet includes the addresscorresponding to the client station 134-1. An address corresponding tothe client station 134-1 includes one or more of i) a unicast addresscorresponding to the client station 134-1, ii) a multicast addresscorresponding to a group of client stations that includes the clientstation 134-1, and/or iii) a broadcast address that corresponds to allclient stations, in various embodiments.

When the wireless network interface device 142 is in the low power stateand receives the wakeup signal from the LP-WUR 150, the wireless networkinterface device 142 is configured to transition to the active powerstate in response to the wakeup signal, according to an embodiment. Forexample, when the wireless network interface device 142 is in the lowpower state and receives the wakeup signal from the LP-WUR 150, thewireless network interface device 142 responsively transitions to theactive power state to become ready to transmit and/or receive, accordingto an embodiment.

The host processor 138 is configured to executed machine readableinstructions stored in a memory device (not shown), according to anembodiment. The host processor 138 is implemented on an IC, according toan embodiment. The wireless network interface device 142 is implementedon one or more ICs. The host processor 138 is implemented on one IC andthe wireless network interface device 142 is implemented on one or moreother, different ICs, according to an embodiment. The host processor 138is implemented on a first IC and the wireless network interface device142 is implemented on at least the same first IC and optionally on oneor more second ICs, according to an embodiment.

The LP-WUR 150 is implemented on one IC and the wireless networkinterface device 142 is implemented on one or more other, different ICs,according to an embodiment. The LP-WUR 150 is implemented on a first ICand the wireless network interface device 142 is implemented on at leastthe same first IC and optionally on one or more second ICs, according toan embodiment.

In an embodiment, each of the client stations 134-2 and 134-3 has astructure that is the same as or similar to the client station 134-1.For example, one or both of the client stations 134-2 and 134-3 includesa respective LP-WUR, according to an embodiment. As another example, oneor both of the client stations 134-2 and 134-3 does not include aLP-WUR, according to another embodiment. Each of the client stations134-2 and 134-3 has the same or a different number of antennas (e.g., 1,2, 3, 4, 5, etc.). For example, the client station 134-2 and/or theclient station 134-3 each have only two antennas (not shown), accordingto an embodiment.

FIG. 1B is a block diagram of the network interface device 122 of the AP114 of FIG. 1A, according to an embodiment. The network interface 122includes a MAC layer processor 160 coupled to a physical layer (PHY)processor 164. The PHY processor 164 includes a plurality oftransceivers 168 coupled to the plurality of antennas 126. Althoughthree transceivers 168 and three antennas 126 are illustrated in FIG.1B, the PHY processor 164 includes other suitable numbers (e.g., 1, 2,4, 5, etc.) of transceivers 168 coupled to other suitable numbers ofantennas 126 in other embodiments. In some embodiments, the AP 114includes a higher number of antennas 126 than transceivers 168, and thePHY processor 164 is configured to use antenna switching techniques.

The network interface 122 is implemented using one or more ICsconfigured to operate as discussed below. For example, the MAC layerprocessor 160 may be implemented, at least partially, on a first IC, andthe PHY processor 164 may be implemented, at least partially, on asecond IC. As another example, at least a portion of the MAC layerprocessor 160 and at least a portion of the PHY processor 164 may beimplemented on a single IC. For instance, the network interface 122 maybe implemented using a system on a chip (SoC), where the SoC includes atleast a portion of the MAC layer processor 160 and at least a portion ofthe PHY processor 164.

In various embodiments, the MAC layer processor 160 and/or the PHYprocessor 164 of the AP 114 are configured to generate data units, andprocess received data units, that conform to a WLAN communicationprotocol such as a communication protocol conforming to the IEEE 802.11Standard or another suitable wireless communication protocol. Forexample, the MAC layer processor 160 may be configured to implement MAClayer functions, including MAC layer functions of the WLAN communicationprotocol, and the PHY processor 164 may be configured to implement PHYfunctions, including PHY functions of the WLAN communication protocol.For instance, the MAC layer processor 160 may be configured to generateMAC layer data units such as MAC service data units (MSDUs), MACprotocol data units (MPDUs), etc., and provide the MAC layer data unitsto the PHY processor 164. The PHY processor 164 may be configured toreceive MAC layer data units from the MAC layer processor 160 andencapsulate the MAC layer data units to generate PHY data units such asPHY protocol data units (PPDUs) for transmission via the antennas 126.Similarly, the PHY processor 164 may be configured to receive PHY dataunits that were received via the antennas 126, and extract MAC layerdata units encapsulated within the PHY data units. The PHY processor 164may provide the extracted MAC layer data units to the MAC layerprocessor 160, which then processes the MAC layer data units.

In connection with generating one or more radio frequency (RF) signalsfor transmission, the PHY processor 164 is configured to process (whichmay include modulating, filtering, etc.) data corresponding to a PPDU togenerate one or more digital baseband signals, and convert the digitalbaseband signal(s) to one or more analog baseband signals, according toan embodiment. Additionally, the PHY processor 164 is configured toupconvert the one or more analog baseband signals to one or more RFsignals for transmission via the one or more antennas 138.

In connection with receiving one or more RF signals, the PHY processor164 is configured to downconvert the one or more RF signals to one ormore analog baseband signals, and to convert the one or more analogbaseband signals to one or more digital baseband signals. The PHYprocessor 164 is further configured to process (which may includedemodulating, filtering, etc.) the one or more digital baseband signalsto generate a PPDU.

The PHY processor 164 includes amplifiers (e.g., a low noise amplifier(LNA), a power amplifier, etc.), a radio frequency (RF) downconverter,an RF upconverter, a plurality of filters, one or more analog-to-digitalconverters (ADCs), one or more digital-to-analog converters (DACs), oneor more discrete Fourier transform (DFT) calculators (e.g., a fastFourier transform (FFT) calculator), one or more inverse discreteFourier transform (IDFT) calculators (e.g., an inverse fast Fouriertransform (IFFT) calculator), one or more modulators, one or moredemodulators, etc.

The PHY processor 164 is configured to generate one or more RF signalsthat are provided to the one or more antennas 126. The PHY processor 164is also configured to receive one or more RF signals from the one ormore antennas 126.

The MAC processor 160 is configured to control the PHY processor 164 togenerate one or more RF signals by, for example, providing one or moreMAC layer data units (e.g., MPDUs) to the PHY processor 164, andoptionally providing one or more control signals to the PHY processor164, according to some embodiments. In an embodiment, the MAC processor160 includes a processor configured to execute machine readableinstructions stored in a memory device (not shown) such as a RAM, a readROM, a flash memory, etc. In an embodiment, the MAC processor 160includes a hardware state machine.

FIG. 1C is a block diagram of the network interface device 142 of theclient station 134-1 of FIG. 1A, according to an embodiment. The networkinterface 142 includes a MAC layer processor 172 coupled to a PHYprocessor 174. The PHY processor 174 includes a plurality oftransceivers 178 coupled to the one or more antennas 146. Although threetransceivers 178 and three antennas 126 are illustrated in FIG. 1C, thePHY processor 174 includes other suitable numbers (e.g., 1, 2, 4, 5,etc.) of transceivers 178 coupled to other suitable numbers of antennas146 in other embodiments. In some embodiments, the client station 134-1includes a higher number of antennas 146 than transceivers 178, and thePHY processor 174 is configured to use antenna switching techniques.

The network interface 142 is implemented using one or more ICsconfigured to operate as discussed below. For example, the MAC layerprocessor 172 may be implemented, at least partially, on a first IC, andthe PHY processor 174 may be implemented, at least partially, on asecond IC. As another example, at least a portion of the MAC layerprocessor 172 and at least a portion of the PHY processor 174 may beimplemented on a single IC. For instance, the network interface 142 maybe implemented using a system on a chip (SoC), where the SoC includes atleast a portion of the MAC layer processor 172 and at least a portion ofthe PHY processor 174.

In various embodiments, the MAC layer processor 172 and the PHYprocessor 174 of the client device 134-1 are configured to generate dataunits, and process received data units, that conform to the WLANcommunication protocol or another suitable communication protocol. Forexample, the MAC layer processor 172 may be configured to implement MAClayer functions, including MAC layer functions of the WLAN communicationprotocol, and the PHY processor 174 may be configured to implement PHYfunctions, including PHY functions of the WLAN communication protocol.The MAC layer processor 172 may be configured to generate MAC layer dataunits such as MSDUs, MPDUs, etc., and provide the MAC layer data unitsto the PHY processor 174. The PHY processor 174 may be configured toreceive MAC layer data units from the MAC layer processor 172 andencapsulate the MAC layer data units to generate PHY data units such asPPDUs for transmission via the one or more antennas 146. Similarly, thePHY processor 174 may be configured to receive PHY data units that werereceived via the one or more antennas 146, and extract MAC layer dataunits encapsulated within the PHY data units. The PHY processor 174 mayprovide the extracted MAC layer data units to the MAC layer processor172, which then processes the MAC layer data units.

As discussed above, the network interface device 142 is configured totransition between an active state and a low power state. When thewireless network interface device 142 is in the low power state andreceives the wakeup signal from the LP-WUR 150, the wireless networkinterface device 142 is configured to transition to the active powerstate in response to the wakeup signal, according to an embodiment.

The PHY processor 174 is configured to downconvert one or more RFsignals received via the one or more antennas 146 to one or morebaseband analog signals, and convert the analog baseband signal(s) toone or more digital baseband signals, according to an embodiment. ThePHY processor 174 is further configured to process the one or moredigital baseband signals to demodulate the one or more digital basebandsignals and to generate a PPDU. The PHY processor 174 includesamplifiers (e.g., an LNA, a power amplifier, etc.), an RF downconverter,an RF upconverter, a plurality of filters, one or ADCs, one or moreDACs, one or more DFT calculators (e.g., a fast Fourier transform (FFT)calculator), one or more IDFT calculators (e.g., an inverse fast Fouriertransform (IFFT) calculator), one or more modulators, one or moredemodulators, etc.

The PHY processor 174 is configured to generate one or more RF signalsthat are provided to the one or more antennas 146. The PHY processor 174is also configured to receive one or more RF signals from the one ormore antennas 146.

The MAC processor 172 is configured to control the PHY processor 174 togenerate one or more RF signals by, for example, providing one or moreMAC layer data units (e.g., MPDUs) to the PHY processor 174, andoptionally providing one or more control signals to the PHY processor174, according to some embodiments. In an embodiment, the MAC processor172 includes a processor configured to execute machine readableinstructions stored in a memory device (not shown) such as a RAM, a readROM, a flash memory, etc. In an embodiment, the MAC processor 172includes a hardware state machine.

FIG. 1D is a block diagram of the LP-WUR 150 of the client station 134-1of FIG. 1A, according to an embodiment. The LP-WUR 150 includes radiofrequency (RF)/analog front-end circuitry 184 coupled to at least one ofthe antennas 146. The RF/analog front-end circuitry 184 includes one ormore amplifiers (e.g., a low noise amplifier (LNA)), an RFdownconverter, one or more filters, and one or more analog-to-digitalconverters (ADCs). In an embodiment, the RF/analog front-end circuitry184 is configured to downconvert an RF signal to a baseband analogsignal, and convert the analog baseband signal to a digital basebandsignal.

The RF/analog front-end circuitry 184 is coupled to digital basebandcircuitry 188. The digital baseband circuitry 188 is configured toprocess the digital baseband signal to determine whether the digitalbaseband signal corresponds to a wakeup packet. The digital basebandcircuitry 188 includes a demodulator that demodulates data from thedigital baseband signal to generate an information signal correspondingto information included in a wakeup packet.

The digital baseband circuitry 188 is coupled to logic circuitry 192.The logic circuitry 192 is configured to process the information signalto determine whether a wakeup packet includes an address (e.g., a MACaddress, an AID, or another suitable network address) corresponding tothe client station 134-1, according to an embodiment. The logiccircuitry 192 is configured to generate the wakeup signal in response todetermining that a received wakeup packet includes the addresscorresponding to the client station 134-1.

FIG. 2 is a block diagram of a wakeup packet 200 used in the exampleWLAN 110 of FIG. 1, according to an embodiment. The network interface122 of the AP 114 is configured to generate and transmit the wakeuppacket 200, according to an embodiment. The network interface 142 of theclient station 134-1 is also configured to generate and transmit thewakeup packet 200, e.g., to prompt another client station 134 to wake upfrom a low power state, according to another embodiment.

The LP-WUR 150 of the client station 134-1 is configured to receive,detect, and decode the wakeup packet 200, according to an embodiment.

The wakeup packet 200 includes an 802.11 preamble portion 204 and apayload 208. The 802.11 preamble portion 204 enables IEEE 802.11stations (e.g., wireless communication devices that are configured tooperate according to the IEEE 802.11 Standard) to detect the wakeuppacket 200 and determine a length of the wakeup packet 200 for thepurpose of reducing transmissions by IEEE 802.11 stations that willcollide with the wakeup packet 200, according to an embodiment.

The 802.11 preamble portion 204 includes a legacy 802.11 preamble 210,which corresponds to a legacy preamble defined by the IEEE 802.11Standard, according to an embodiment. The legacy 802.11 preamble 210includes a legacy short training field (L-STF) 212, a legacy longtraining field (L-LTF) 216, a legacy signal field (L-SIG) 220. The L-STF212 includes signals designed for packet detection and automatic gaincontrol (AGC) training. The L-LTF 216 includes signals designed forchannel estimation and synchronization. The L-SIG 220 includesinformation regarding the wakeup packet 200, including lengthinformation (e.g., in a length subfield (not shown)) that can be used byIEEE 802.11 stations to determine when the wakeup packet 200 will end.

In other embodiments, the wakeup packet 200 includes a legacy preamble(different than the legacy 802.11 preamble 210) that enables stationsthat conform to a different suitable wireless communication protocol(e.g., other than the IEEE 802.11 Standard) to detect the wakeup packet200 and determine a length of the wakeup packet 200 for the purpose ofreducing transmissions by such stations that will collide with thewakeup packet 200, according to an embodiment.

In an embodiment, the 802.11 preamble portion 204 also includes a binaryphase shift keying (BPSK) modulated field (BPSK-modulated field) 224that follows the legacy 802.11 preamble 210. In an embodiment, theBPSK-modulated field 224 is a repetition of the L-SIG 220. In anembodiment, the BPSK-modulated field 224 is identical to at least aportion of the L-LTF 216. In other embodiments, the BPSK-modulated field224 includes any other suitable signal and/or information. In anembodiment, the BPSK-modulated field 224 does not convey any usefulinformation to recipient communication devices. In another embodiment,the BPSK-modulated field 224 does convey useful information to recipientcommunication devices. For example, in an embodiment, wakeup packet data(e.g., which includes a network address corresponding to an intendedclient station or stations) is encoded within/on a set of OFDM symbolsthat includes the BPSK-modulated field 224 and the payload 208. In someembodiments, the BPSK-modulated field 224 is omitted from the wakeuppacket 200.

The payload 208 includes a wakeup preamble 228. In an embodiment, thewakeup preamble 228 includes signals that enable LP-WURs such as theLP-WUR 150 to detect the payload 208 of the wakeup packet 200 and tosynchronize to the payload 208 of the wakeup packet 200. The payload 208also includes a wakeup packet data portion 232. In an embodiment, thewakeup packet data portion 232 includes an address (e.g., a MAC address,an AID, or another suitable network address) corresponding to a clientstation (or client stations) to which the wakeup packet 200 is intended.Referring now to FIG. 1D, the digital baseband circuitry 188 isconfigured to detect the wakeup packet 200 at least by detecting thewakeup preamble 228, according to an embodiment. The logic circuitry 192is configured to process the wakeup packet body 232 to determine whetherthe wakeup packet body 232 includes an address (e.g., a MAC address, anAID, or another suitable network address) corresponding to the clientstation 134-1.

In an embodiment, the legacy 802.11 preamble 210 spans a first frequencybandwidth, and the wakeup preamble 228 and the wakeup packet dataportion 232 span a second frequency bandwidth that is narrower than thefirst frequency bandwidth. For example, the first frequency bandwidth is20 MHz and the second frequency bandwidth is a narrower bandwidth suchas approximately 4 MHz (e.g. 4.06 MHz), or another suitable narrowerbandwidth such as 1 MHz, 2 MHz, 5 MHz, 10 MHz, etc.

FIG. 3A is a diagram of an example payload portion 300 of a wakeuppacket, such as the wakeup packet 200 of FIG. 2, according to anembodiment. The payload portion 300 is used as the payload 208 of thewakeup packet 200 of FIG. 2, according to an embodiment. FIG. 3A isdescribed in the context of the wakeup packet 200 of FIG. 2 forexplanatory purposes. In other embodiments, however, the payload portion300 is included in another suitable wakeup packet different that thewakeup packet 200 of FIG. 2.

The payload portion 300 includes a WUR preamble 304 and the wakeuppacket data portion 232 (FIG. 2). The WUR preamble 304 includes a WURsync portion 308 and a WUR PHY header portion 312. The WUR sync portion308 is used by a wakeup radio (e.g., the LP-WUR 150 of FIG. 1) for oneor more of carrier sensing, detection of the payload portion 300,synchronization to the payload portion 300, etc. The WUR PHY headerportion 312 includes information regarding the payload portion 300 thatis used by a wakeup radio (e.g., the LP-WUR 150 of FIG. 1) to processthe wakeup packet data portion 232 (FIG. 2). The information regardingthe payload portion 300 in the WUR PHY header portion 312 includes PHYparameter signaling, such as one or more of a data rate at which thewakeup packet data portion 232 is encoded, a modulation schemed used forthe wakeup packet data portion 232, a coding scheme used for the wakeuppacket data portion 232, a length/duration of the wakeup packet dataportion 232, etc.

In an embodiment, the WUR preamble 304 is modulated/encoded according toa first, lowest data rate defined by a communication protocol, whereasthe wakeup packet data portion 232 is modulated/encoded according to asecond data rate defined by the communication protocol, where the seconddata rate is selected from a plurality of data rates defined by thecommunication protocol, which includes one or more data rates that arehigher than the first data rate. The WUR PHY header portion 312 includesinformation that indicates the second data rate, according to anembodiment.

FIG. 3B is a diagram of another example payload portion 350 of a wakeuppacket, such as the wakeup packet 200 of FIG. 2, according to anotherembodiment. The payload portion 350 is used as the payload 208 of thewakeup packet 200 of FIG. 2, according to an embodiment. FIG. 3B isdescribed in the context of the wakeup packet 200 of FIG. 2 forexplanatory purposes. In other embodiments, however, the payload portion350 is included in another suitable wakeup packet different that thewakeup packet 200 of FIG. 2.

The payload portion 350 includes a WUR sync portion 354 and a WUR PHYheader portion 358. The WUR sync portion 354 is used by a wakeup radio(e.g., the LP-WUR 150 of FIG. 1) for one or more of carrier sensing,detection of the payload portion 300, synchronization to the payloadportion 300, etc. The WUR sync portion 354 also indicates one or morePHY parameters, such as one or more of a data rate at which the wakeuppacket data portion 232 is encoded, a modulation schemed used for thewakeup packet data portion 232, a coding scheme used for the wakeuppacket data portion 232, etc., and is used by a wakeup radio (e.g., theLP-WUR 150 of FIG. 1) to process the WUR PHY header portion 358 and/orthe wakeup packet data portion 232 (FIG. 2). For example, the WUR syncportion 354 may include a sync pattern selected from a plurality of syncpatterns, wherein sync patterns from among the plurality of syncpatterns indicate one or more of respective data rates, respectivemodulation schemes, respective coding rates, etc.

The WUR PHY header portion 358 includes information regarding thepayload portion 300 that is used by a wakeup radio (e.g., the LP-WUR 150of FIG. 1) to process the wakeup packet data portion 232 (FIG. 2). Theinformation regarding the payload portion 300 in the WUR PHY headerportion 358 includes PHY parameter signaling, such as one or more of adata rate at which the wakeup packet data portion 232 is encoded, amodulation schemed used for the wakeup packet data portion 232, a codingscheme used for the wakeup packet data portion 232, a length/duration ofthe wakeup packet data portion 232, etc.

In an embodiment, the WUR sync portion 354 is modulated/encodedaccording to the first, lowest data rate defined by the communicationprotocol, whereas the WUR PHY header portion and the wakeup packet dataportion 232 are modulated/encoded according to a second data ratedefined by the communication protocol, where the second data rate isselected from a plurality of data rates defined by the communicationprotocol, which includes one or more data rates that are higher than thefirst data rate. The WUR sync portion 354 indicates the second datarate, according to an embodiment.

In some embodiments in which the WUR sync portion 354 indicates one ormore PHY parameters, such as one or more of a data rate at which thewakeup packet data portion 232 is encoded, a modulation schemed used forthe wakeup packet data portion 232, a coding scheme used for the wakeuppacket data portion 232, etc., the WUR PHY header portion 358 is omittedfrom the payload portion 350.

FIG. 4 is a diagram of an example WUR sync portion 400, according to anembodiment. The WUR sync portion 400 is used in a WUR packet such asthose described above with reference to FIGS. 2, 3A, and 3B, or anothersuitable WUR packet, in various embodiments.

The WUR sync portion 400 includes N sync sequences 404, where N is asuitable integer greater than two. Each sync sequence 404 is sometimesreferred to herein as a sync symbol 404.

Each sync sequence 404 has a length of K samples corresponding to asuitable sampling rate, wherein K is a suitable integer greater thantwo. Generally, as the value of N increases, a carrier sensing (CS)property of the sync sequence 404 improves and a symbol timingacquisition (ST) property of the sync sequence 404 improves, at least insome embodiments. Generally, as the value of K increases, a correlationproperty of the sync sequence 404 improves, at least in someembodiments. Generally, as N and K increase, the length of the WUR syncportion 400 increases, which adversely affects efficiency because morechannel time is consumed transmitting the WUR sync portion 400 ratherthan user data, at least in some embodiments.

In some embodiments, the WUR sync portion 400 is modulated according toon-off keying (OOK). For example, in some embodiments, each syncsequence 404 is selected from a set consisting of two sync symbols: i) apredetermined sequence corresponding to “On” (O), and ii) a zero energysequence (e.g., a sequence of zeros) corresponding to “Off” (F). Thus,as an illustrative example in which N is four, the WUR sync portion 400comprises OOOF. As another illustrative example in which N is four, theWUR sync portion 400 comprises OFOF. As an illustrative example in whichN is five, the WUR sync portion 400 comprises OOOOF. As anotherillustrative example in which N is five, the WUR sync portion 400comprises OOFOF. As an illustrative example in which N is six, the WURsync portion 400 comprises OOOOOF. As another illustrative example inwhich N is six, the WUR sync portion 400 comprises OFOFOF.

In other embodiments, each sync sequence 404 is selected from a setconsisting of three sync symbols: i) a predetermined sequencecorresponding to “On” (O), ii) a zero energy sequence (e.g., a sequenceof zeros) corresponding to “Off” (F), and iii) the predeterminedsequence phase rotated by 180 degrees corresponding to “Negative On”(M). Thus, as an illustrative example in which N is five, the WUR syncportion 400 comprises OOMOF. As another illustrative example in which Nis five, the WUR sync portion 400 comprises OOMOM.

In some embodiments, the WUR sync portion 400 is modulated according toOOK combined with Manchester coding. For example, in some embodiments,each sync sequence 404 is selected from a set consisting of two syncsymbols: i) a first sequence comprising a) a first occurring half (intime) set to a predetermined sequence, and b) a second occurring half(in time) set to a zero energy sequence (e.g., a sequence of zeros) “On”(O); and ii) a second sequence comprising a) a first occurring half (intime) set to a zero energy sequence (e.g., a sequence of zeros), and b)a second occurring half (in time) set to a predetermined sequence “Off”(F). Thus, as an illustrative example in which N is four, the WUR syncportion 400 comprises OOOF. As another illustrative example in which Nis four, the WUR sync portion 400 comprises OFOF. As an illustrativeexample in which N is five, the WUR sync portion 400 comprises OOOOF. Asanother illustrative example in which N is five, the WUR sync portion400 comprises OOFOF. As an illustrative example in which N is six, theWUR sync portion 400 comprises OOOOOF. As another illustrative examplein which N is six, the WUR sync portion 400 comprises OFOFOF.

In some embodiments, each sync sequence 404 is selected from a setconsisting of two sync symbols: i) a predetermined sequence (SYNC), andii) the predetermined sequence phase rotated by 180 degrees (−SYNC),wherein the predetermined sequence (SYNC) comprises a plurality ofmodulated subsymbols. For instance, each subsymbol is modulatedaccording to a suitable modulation scheme such as BPSK, quadrature phaseshift keying (QPSK), etc., according to various embodiments.

The predetermined sequence (SYNC) is selected to have an autocorrelationfunction that resembles an impulse function (e.g., a relatively highcenter peak as compared to heights of side lobes, where the center peakis also relatively narrow, e.g., as compared to a height of the centerpeak). In an embodiment, the predetermined sequence (SYNC) is selectedto have a zero direct current (DC) component. In an embodiment, anexhaustive search technique is used to determine a predeterminedsequence (SYNC) with suitable autocorrelation and DC componentproperties. In one illustrative embodiment, the predetermined sequence(SYNC) is:

-   -   [−1 −1 1 −1 1 −1 1 1 −1 −1 1 1 1 1 −1 −1]        In other embodiments, the predetermined sequence (SYNC) is        another suitable sequence.

As an illustrative embodiment in which N is four, the WUR sync portion400 comprises [SYNC SYNC SYNC −SYNC]. As another illustrative embodimentin which N is six, the WUR sync portion 400 comprises [SYNC SYNC SYNCSYNC −SYNC −SYNC].

In some embodiments, each sync sequence 404 comprises one or more Golaysequences Ga. In some embodiments, each sync sequence 404 comprises oneor more Golay sequences Ga, and one or more Golay sequences Gb, whereinthe Golay sequence Gb is a complementary sequence to the Golay sequenceGa. Generally, the two complementary Golay sequences Ga and Gb havecorrelation properties suitable for detection at a receiving device. Forexample, the complementary Golay sequences Ga and Gb may be selected sothat the sum of corresponding out-of-phase aperiodic autocorrelationcoefficients of the sequences Ga and Gb is zero. In some embodiments,the complementary sequences Ga and Gb have a zero or almost-zeroperiodic cross-correlation. In another aspect, the sequences Ga and Gbmay have aperiodic cross-correlation with a narrow main lobe andlow-level side lobes, or aperiodic auto-correlation with a narrow mainlobe and low-level side lobes.

In an embodiment, Ga (or, Ga and Gb) is/are selected to have a smallestDC component. In an embodiment, Ga is selected to have a duration of 2microseconds. In another embodiment, Ga (or, Ga and Gb) are selected tohave a duration of 2 microseconds. In another embodiment, Ga (or, Ga andGb) are selected to have a duration of 4 microseconds.

In some embodiments utilizing Golay sequences, each sync sequence 404 isselected from a set consisting of two sync symbols: i) Ga, and ii) Garotated by 180 degrees (−Ga). For example, in an embodiment, the WURsync portion 400 comprises a plurality of consecutive sequences Ga, anda last occurring sync sequence 404 comprising −Ga. As an illustrativeembodiment in which N is four, the WUR sync portion 400 comprises [Ga GaGa −Ga]. As an illustrative embodiment in which N is five, the WUR syncportion 400 comprises [Ga Ga Ga Ga −Ga].

In some embodiments utilizing Golay sequences, each sync sequence 404 isselected from a set consisting of two sync symbols: i) Ga, and ii) Gb.For example, in an embodiment, the WUR sync portion 400 comprises aplurality of consecutive sequences Ga, and a last occurring syncsequence 404 comprising Gb. As an illustrative embodiment in which N isfour, the WUR sync portion 400 comprises [Ga Ga Ga Gb]. As anillustrative embodiment in which N is five, the WUR sync portion 400comprises [Ga Ga Ga Ga Gb].

In some embodiments utilizing Golay sequences, each sync sequence 404 isselected from a set consisting of two sync symbols: i) [Ga Gb], and ii)[−Ga −Gb]. For example, in an embodiment, the WUR sync portion 400comprises one or more consecutive sequences [Ga Gb], and a lastoccurring sync sequence 404 comprising [−Ga −Gb]. As an illustrativeembodiment in which N is three, the WUR sync portion 400 comprises [GaGb Ga Gb −Ga −Gb].

In some embodiments utilizing Golay sequences, each sync sequence 404 isselected from a set consisting of two sync symbols: i) [Ga Ga Gb Gb],and ii) [−Ga −Ga −Gb −Gb]. For example, in an embodiment, the WUR syncportion 400 comprises one or more consecutive sequences [Ga Ga Gb Gb],and a last occurring sync sequence 404 comprising [−Ga −Ga −Gb −Gb]. Asan illustrative embodiment in which N is three, the WUR sync portion 400comprises [Ga Ga Gb Gb −Ga −Ga −Gb −Gb].

Referring again to FIGS. 3A and 3B, in some embodiments in which a WURsync portion (e.g., the WUR sync portion 308, the WUR sync portion 354)of a wakeup packet signals one or more PHY parameters corresponding tothe data portion 232 (e.g., a data rate, a modulation scheme, a codingscheme, a length/duration, etc.), different WUR sync portion contentscorrespond to different PHY modes, wherein the different sync portioncontents are included in a set of candidate WUR sync portions. In suchembodiments, a candidate WUR sync portion is selected from the set ofcandidate WUR sync portions according to the PHY mode that is to be usedto transmit the data portion 232 of the wakeup packet.

FIG. 5A is a diagram of a WUR sync portion selection device 500,according to an embodiment. The WUR sync portion selection device 500 isincluded in a network interface such as the network interface 122 ofFIGS. 1A and 1B, in an embodiment. The WUR sync portion selection device500 is included in the PHY processor 164, in an embodiment.

The WUR sync portion selection device 500 includes a multiplexer 504. Aplurality of candidate WUR sync portions are provided to a plurality ofinputs of the multiplexer 504. In an embodiment, candidate WUR syncportions are stored in respective registers, and the registers arecoupled to respective inputs of the multiplexer 504. A control signal isprovided to a control input of the multiplexer 504. The control signalindicates a PHY mode that is to be used to transmit the data portion 232of the wakeup packet. The control signal causes the multiplexer 504 tocouple a selected one of the multiplexer inputs to an output of themultiplexer 504.

In other embodiments, the WUR sync portion selection device 500 isimplemented using a hardware state machine. For example, the hardwarestate machine is coupled to a memory device that stores the plurality ofcandidate WUR sync portions in respective locations of the memorydevice, in an illustrative embodiment. The control signal causes thehardware state machine to select one of the locations of the memorydevice to read out a selected WUR sync portion from the memory device.

In other embodiments, the WUR sync portion selection device 500 isimplemented using a processor executing machine readable instructions.For example, the processor is coupled to a memory device that stores theplurality of candidate WUR sync portions in respective locations of thememory device, in an illustrative embodiment. The machine readableinstructions, when executed by the processor, cause the processor toselect one of the locations of the memory device to read out a selectedWUR sync portion from the memory device.

Referring again to FIGS. 3A and 3B, in some embodiments in which a WURsync portion (e.g., the WUR sync portion 308, the WUR sync portion 354)of a wakeup packet signals one or more PHY parameters corresponding tothe data portion 232 (e.g., a data rate, a modulation scheme, a codingscheme, a length/duration, etc.), different SYNC symbols correspond todifferent PHY modes, wherein the different SYNC symbols are included ina set of candidate SYNC symbols. In such embodiments, a candidate SYNCsymbol is selected from the set of candidate SYNC symbols according tothe PHY mode that is to be used to transmit the data portion 232 of thewakeup packet. The selected SYNC portion is then used to generate theWUR sync portion.

FIG. 5B is a diagram of a SYNC symbol selection device 550, according toan embodiment. The SYNC symbol selection device 550 is included in anetwork interface such as the network interface 122 of FIGS. 1A and 1B,in an embodiment. The SYNC symbol selection device 500 is included inthe PHY processor 164, in an embodiment.

The SYNC symbol selection device 500 includes a multiplexer 554. Aplurality of candidate SYNC symbols are provided to a plurality ofinputs of the multiplexer 554. In an embodiment, candidate SYNC symbolsare stored in respective registers, and the registers are coupled torespective inputs of the multiplexer 554. A control signal is providedto a control input of the multiplexer 554. The control signal indicatesa PHY mode that is to be used to transmit the data portion 232 of thewakeup packet. The control signal causes the multiplexer 554 to couple aselected one of the multiplexer inputs to an output of the multiplexer504.

In other embodiments, the SYNC symbol selection device 550 isimplemented using a hardware state machine. For example, the hardwarestate machine is coupled to a memory device that stores the plurality ofcandidate SYNC symbols in respective locations of the memory device, inan illustrative embodiment. The control signal causes the hardware statemachine to select one of the locations of the memory device to read outa selected SYNC symbol from the memory device.

In other embodiments, the SYNC symbol selection device 500 isimplemented using a processor executing machine readable instructions.For example, the processor is coupled to a memory device that stores theplurality of candidate SYNC symbols in respective locations of thememory device, in an illustrative embodiment. The machine readableinstructions, when executed by the processor, cause the processor toselect one of the locations of the memory device to read out a selectedSYNC symbol from the memory device.

FIG. 6 is a flow diagram of an example method 600 for generating wakeuppackets, according to an embodiment. In some embodiments, the networkinterface device 122 of FIG. 1 is configured to implement the method600. The method 600 is described in the context of the network interfacedevice 122 merely for explanatory purposes and, in other embodiments,the method 600 is implemented by another suitable device, such as thenetwork interface device 142 or another suitable network interfacedevice.

At block 604, the network interface device 122 generates (e.g., the PHYprocessor 164 generates) a first portion of a wakeup packet. The firstportion corresponds to a legacy PHY preamble corresponding to acommunication protocol. The first portion spans a first bandwidth. In anembodiment, the legacy PHY preamble is a legacy 802.11 preamblecorresponding to the protocol specified by the IEEE 802.11n Standard.The legacy PHY preamble corresponds to other communication protocols aswell, such as the protocol specified by the IEEE 802.11ac Standard, theprotocol specified by the IEEE 802.11ax Standard (now underdevelopment), etc., in some embodiments.

At block 608, the network interface device 122 generates a secondportion of the wakeup packet. The second portion spans a secondbandwidth that is less than the first bandwidth. The second portion ofthe wakeup packet is configured to prompt one or more wakeup radios atone or more respective communication devices to prompt one or morerespective network interfaces to transition from a low power state to anactive state. According to an embodiment, the second portion of thewakeup packet does not conform to the communication protocol to whichthe legacy PHY preamble conforms.

In some embodiments, generating the second portion of the wakeup packetincludes generating a sync portion having a plurality of sync symbols.In an embodiment, the sync portion is modulated according to OOK, andeach sync symbol is selected from a set consisting of i) a non-zeroenergy sequence, and ii) a zero energy sequence. In another embodimentin which the sync portion is modulated according to OOK, each syncsymbol is selected from a set consisting of i) a non-zero energysequence, ii) the non-zero energy sequence phase rotated by 180 degrees,and iii) a zero energy sequence.

In an embodiment, the sync portion is modulated according to aManchester code, and each sync symbol is selected from a set consistingof i) a first sync symbol comprising a) a first occurring non-zeroenergy portion, and b) a second occurring zero energy portion; and ii) asecond sync symbol comprising a) a first occurring zero energy portion,and b) a second occurring non-zero energy portion.

In another embodiment, each sync symbol is selected from a setconsisting of i) a non-zero energy sequence, and ii) the non-zero energysequence phase rotated by 180 degrees.

In another embodiment, each sync symbol comprises one or more Golaycodes.

Generating the second portion of the wakeup packet further includesgenerating a wakeup packet body.

In an embodiment, the second portion of the wakeup packet is notconfigured to be decoded and processed by a network interface devicethat can decode and process data units conforming to a standard withinthe IEEE 802.11 Standard family.

At block 612, the network interface device 122 transmits the wakeuppacket.

In some embodiments, the method 600 further includes determining, at thenetwork interface device 122, a PHY mode according to which the wakeuppacket body is to be transmitted; and selecting the sync portion from aset of candidate sync portions according to the selected PHY mode,wherein the selected sync portion indicates the PHY mode.

In some embodiments, the method 600 further includes determining, at thenetwork interface device 122, a PHY mode according to which the wakeuppacket body is to be transmitted; and selecting the sync symbol from aset of candidate sync symbol according to the selected PHY mode, whereinthe selected sync symbol indicates the PHY mode.

Referring again to FIGS. 1B and 4, the LP-WUR 150 (e.g., the digitalbaseband circuitry 188) includes a WUR preamble detector that isconfigured to i) detect a WUR preamble portion (e.g., the WUR preambleportion 400) in a wakeup packet (sometimes referred to herein as carriersensing (CS)), and ii) determine a symbol timing (ST) of the wakeuppacket using the WUR preamble portion. The WUR preamble detectorincludes one or more correlators (e.g., autocorrelators,cross-correlators, etc.) that compute one or more correlationscorresponding to sync symbols in the WUR preamble portion, according toan embodiment. For example, the one or more correlators are configuredto detect sync symbols in the WUR preamble portion, according to anembodiment. The WUR preamble detector is configured to use one or moreoutputs of one or more correlators to detect a pattern of sync symbolsin a received signal that matches a pattern of sync symbols in the WURpreamble portion. Detection of the pattern of sync symbols in thereceived signal indicates that the received signal includes the WURpreamble portion, according to an embodiment.

In some embodiments, the WUR preamble detector is configured to use oneor more outputs of one or more correlators to a symbol timing of syncsymbols in a received signal that includes the WUR preamble portion. Forexample, the WUR preamble detector is configured to estimate centers ofpeaks in the one or more outputs of the one or more correlators, and touse the estimated centers of the peaks to determine the symbol timing ofsync symbols in the received signal, according to an embodiment.

In some embodiments in which the sync symbols include zero power syncsymbols (e.g., OOK-modulated WUR preamble portions) or portions of syncsymbols corresponding to a zero power sync signal (e.g., Manchestercode-modulated WUR preamble portions), the WUR preamble detector isconfigured to measure one or more energy levels at one or more expectedlocations of zero power signals in the WUR sync portion. For example,the WUR preamble detector includes one or more energy level measurementcircuits, and the WUR preamble detector uses outputs of the one or moreenergy level measurement circuits to detect energy levels that fallbelow a threshold at one or more expected locations of zero powersignals in the WUR sync portion. In some embodiments, the WUR preambledetector uses outputs of the one or more energy level measurementcircuits to detect one or more transitions at expected locations in theWUR sync portion where the WUR sync portion is configured to transitionfrom a non-zero energy signal to a zero energy signal, or vice versa.

For example, with OOK-modulated WUR preamble portions, the WUR preambledetector includes one or more correlators (e.g., autocorrelators,cross-correlators, etc.) that compute one or more correlationscorresponding to O (and/or M) locations in the WUR preamble portion,according to an embodiment. Also with OOK-modulated WUR preambleportions, the WUR preamble detector includes one or more energydetectors that generate one or more energy measurements corresponding toF locations in the WUR preamble portion, according to an embodiment.

For example, the WUR preamble detector compares the one or morecorrelations to one or more respective first thresholds to generate oneor more correlation peak detection signals, according to an embodiment.As another example, the WUR preamble detector compares the one or moreenergy measurements to one or more respective second thresholds togenerate one or more energy detection signals, according to anembodiment. As an illustrative embodiment, the WUR preamble detectorcompares an energy measurement to two second thresholds (an O secondthreshold and an F second threshold) to generate an energy detectionsignal that indicates when a signal energy as i) exceeded the O secondthreshold (corresponding to an expected O location), and ii) then fallenbelow the F second threshold (corresponding to an expected F location),according to an embodiment.

FIG. 7 is a block diagram of an example WUR preamble detector 700,according to an embodiment. The WUR preamble detector 700 is for usewith the OOK-modulated WUR preamble portion 400 when the OOK-modulatedWUR preamble portion 400 comprises five symbols: OOOOF.

The WUR preamble detector 700 comprises an autocorrelation calculator704 coupled to three delay elements 708, which are coupled together inseries. An output of the delay element 708-1 corresponds to anautocorrelation between a fourth occurring symbol in the OOK-modulatedWUR preamble portion 400, and a third occurring symbol in theOOK-modulated WUR preamble portion 400. An output of the delay element708-2 corresponds to an autocorrelation between the third occurringsymbol in the OOK-modulated WUR preamble portion 400, and a secondoccurring symbol in the OOK-modulated WUR preamble portion 400. Anoutput of the delay element 708-3 corresponds to an autocorrelationbetween the second occurring symbol in the OOK-modulated WUR preambleportion 400, and a first occurring symbol in the OOK-modulated WURpreamble portion 400.

The WUR preamble detector 700 also comprises an energy measurementdevice 712. An output of the energy measurement device 712 correspondsto an energy measurement of a fifth occurring symbol in theOOK-modulated WUR preamble portion 400.

The WUR preamble detector 700 also comprises logic 720, which is coupledto the output of the delay element 708-1, the output of the delayelement 708-2, the output of the delay element 708-3, and the output ofthe energy measurement device 712. In an embodiment, the logic 720includes three respective first comparators that are configured tocompare the output of the delay element 708-1, the output of the delayelement 708-2, and the output of the delay element 708-3 to respectivefirst thresholds. For example, when the logic 720 determines the outputof the delay element 708-1, the output of the delay element 708-2, andthe output of the delay element 708-1 all exceed the respective firstthresholds, this indicates that the received signal includes fourconsecutive O symbols.

In another embodiment, the logic 720 includes an adder that sums theoutput of the output of the delay element 708-1, the output of the delayelement 708-2, and the output of the delay element 708-3. The logic 720also includes one first comparator that compares an output of the adderto one first threshold. For example, when the logic 720 determines theoutput of the adder exceeds the first threshold, this indicates that thereceived signal includes four consecutive O symbols.

In an embodiment, the logic 720 includes two second comparators thatcompare the output of the energy measurement device 712 to two secondthresholds (an O second threshold and an F second threshold). When thelogic 720 determines that the output of the energy measurement device712 i) first exceeds the O second threshold (corresponding to the fourthsymbol in the preamble), and ii) then falls below the F second threshold(corresponding to the fifth location in the preamble), this indicatesthat the received signal includes an O symbol followed by an F symbol,according to an embodiment.

When the logic determines i) that the received signal includes fourconsecutive O symbols corresponding to the first, second, third, andfourth symbol locations in the preamble (OOOOF), and ii) that thereceived signal includes an O symbol (at the fourth symbol location)followed by an F symbol (at the fifth symbol location), the logic 720determines that the preamble (OOOOF) has been detected, generates acarrier sense (CS) signal to indicate that the preamble (OOOOF) has beendetected.

Additionally, the logic 720 estimates the centers of peaks in one ormore of the output of the autocorrelation calculator 704, the output ofthe delay element 708-1, the output of the delay element 708-2, and theoutput of the delay element 708-3 to estimate the centers of symbols inthe preamble (OOOOF), according to an embodiment. The logic 720 uses theestimated centers of symbols in the preamble (OOOOF) to generate asymbol timing (ST) signal that indicates the centers of symbols in thepreamble (OOOOF), according to an embodiment.

In an embodiment, the logic 720 comprises hardware circuitry (e.g., oneor more comparator circuits, one or more adder circuits, one or morestate machine circuits, etc.) configured to implement the functionsdescribed above. In another embodiment, the logic 720 is implementedusing a processor executing machine readable instructions stored in amemory device, wherein the machined readable instructions, when executedby the processor, cause the processor to implement the functionsdescribed above. In another embodiment, the logic 720 comprises acombination of i) hardware circuitry (e.g., one or more comparatorcircuits, one or more adder circuits, one or more state machinecircuits, etc.) and ii) a processor executing machined readableinstructions, that together implement the functions described above.

Although the example WUR preamble detector 700 includes a singleautocorrelator 704, the WUR preamble detector 700 includes multipleautocorrelators corresponding to multiple locations in the WUR syncportion at which two consecutive O symbols occur, in another embodiment.In other embodiments, the autocorrelator 704 (and/or one or more otherautocorrelators) in the WUR preamble detector 700 are replaced with oneor more cross-correlators that are configured to cross-correlate thereceived signal with one or more local copies of sync symbols in the WURsync portion.

With Manchester code encoded WUR preamble portions, the WUR preambledetector includes one or more correlators (e.g., autocorrelators,cross-correlators, etc.) that compute one or more correlationscorresponding to locations in the WUR preamble portion at which anon-zero energy signal is present, according to an embodiment. Also withManchester code encoded WUR preamble portions, the WUR preamble detectorincludes one or more energy detectors that generate one or more energymeasurements corresponding to locations in the WUR sync portion at whichthe zero energy signal is present, according to an embodiment.

In embodiments in which the WUR sync portion is modulated using atechniques other than OOK or Manchester code encoding, the WUR preambledetector includes one or more correlators (e.g., autocorrelators,cross-correlators, etc.) that compute one or more correlationscorresponding to locations of sync symbols in the WUR sync portion. Forexample, if the WUR sync portion includes two consecutive sync symbolswith a same signal, the WUR preamble detector uses an autocorrelation todetect two consecutive sync symbols in a received signal, according toan embodiment. Additionally or alternatively, the WUR preamble detectoruses a cross-correlation to detect a sync symbol in a received signal,according to an embodiment.

FIG. 8 is a block diagram of another example WUR preamble detector 800,according to another embodiment. The WUR preamble detector 800 is foruse with a Golay code-modulated WUR preamble portion 400 when the Golaycode-modulated WUR preamble portion 400 comprises four symbols: Ga Ga GaGb.

The WUR preamble detector 800 comprises a first cross-correlationcalculator 804 coupled to three delay elements 808, which are coupledtogether in series. The first cross-correlation calculator 804 isconfigured to compute a cross-correlation between a received signal andthe Golay code Ga. An output of the delay element 808-1 corresponds to across-correlation between a third occurring symbol in the WUR preambleportion 400 and Ga. An output of the delay element 808-2 corresponds toa cross-correlation between a second occurring symbol in the WURpreamble portion 400 and Ga. An output of the delay element 808-3corresponds to a cross-correlation between a first occurring symbol inthe WUR preamble portion 400 and Ga.

The WUR preamble detector 800 also comprises a second cross-correlationcalculator 812. The second cross-correlation calculator 812 isconfigured to compute a cross-correlation between the received signaland the Golay code Gb. An output of the second cross-correlationcalculator 812 corresponds to a cross-correlation between a fourthoccurring symbol in the WUR preamble portion 400 and Gb.

The WUR preamble detector 800 also comprises logic 820, which is coupledto the output of the delay element 808-1, the output of the delayelement 808-2, the output of the delay element 808-3, and the output ofthe second cross-correlation calculator 812. In an embodiment, the logic820 includes three respective first comparators that are configured tocompare the output of the delay element 808-1, the output of the delayelement 808-2, and the output of the delay element 808-3 to respectivefirst thresholds. For example, when the logic 820 determines the outputof the delay element 808-1, the output of the delay element 808-2, andthe output of the delay element 808-3 all exceed the respective firstthresholds, this indicates that the received signal includes threeconsecutive Ga symbols.

In another embodiment, the logic 820 includes an adder that sums theoutput of the output of the delay element 808-1, the output of the delayelement 808-2, and the output of the delay element 808-3. The logic 820also includes one first comparator that compares an output of the adderto one first threshold. For example, when the logic 820 determines theoutput of the adder exceeds the first threshold, this indicates that thereceived signal includes three consecutive Ga symbols.

In an embodiment, the logic 820 includes a second comparator thatcompares the output of the second cross-correlation calculator 812 to asecond threshold. When the logic 820 determines that the output of thesecond cross-correlation calculator 812 exceeds the second threshold,this indicates that the received signal includes the Gb symbol,according to an embodiment.

In another embodiment, the logic 820 includes an adder that sums theoutput of the output of the delay element 808-1, the output of the delayelement 808-2, the output of the delay element 808-3, and the output ofthe second cross-correlation calculator 812. The logic 820 also includesone comparator that compares an output of the adder to a threshold. Forexample, when the logic 820 determines the output of the adder exceedsthe threshold, this indicates that the received signal includes threeconsecutive Ga symbols followed by a Gb symbol.

When the logic determines i) that the received signal includes threeconsecutive Ga symbols corresponding to the first, second, and thirdsymbol locations in the preamble, and ii) that the received signalincludes a Gb symbol at the fourth symbol location, the logic 820determines that the preamble (Ga Ga Ga Gb) has been detected, andgenerates a carrier sense (CS) signal to indicate that the preamble (GaGa Ga Gb) has been detected.

Additionally, the logic 820 estimates the centers of peaks in one ormore of the output of the first cross-correlation calculator 804, theoutput of the delay element 808-1, the output of the delay element808-2, the output of the delay element 808-3, and the output of thesecond cross-correlation calculator 812 to estimate the centers ofsymbols in the preamble, according to an embodiment. The logic 820 usesthe estimated centers of symbols in the preamble to generate a symboltiming (ST) signal that indicates the centers of symbols in thepreamble, according to an embodiment.

In an embodiment, the logic 820 comprises hardware circuitry (e.g., oneor more comparator circuits, one or more adder circuits, one or morestate machine circuits, etc.) configured to implement the functionsdescribed above. In another embodiment, the logic 820 is implementedusing a processor executing machine readable instructions stored in amemory device, wherein the machined readable instructions, when executedby the processor, cause the processor to implement the functionsdescribed above. In another embodiment, the logic 820 comprises acombination of i) hardware circuitry (e.g., one or more comparatorcircuits, one or more adder circuits, one or more state machinecircuits, etc.) and ii) a processor executing machined readableinstructions, that together implement the functions described above.

Although the example WUR preamble detector 800 includes a single firstcross-correlation calculator 804, the WUR preamble detector 800 includesmultiple first cross-correlation calculators 804 corresponding tomultiple locations in the WUR sync portion at which Ga symbols occur, inanother embodiment. In other embodiments, the first cross-correlationcalculator 804 is replaced with one or more autocorrelators that areconfigured to generate an autocorrelation of the received signal todetect two consecutive Ga symbols in the received signal.

FIG. 9 is a block diagram of another example WUR preamble detector 900,according to another embodiment. The WUR preamble detector 900 is foruse with a Golay code-modulated WUR preamble portion 400 when the Golaycode-modulated WUR preamble portion 400 comprises four symbols: Ga Ga GbGb.

The WUR preamble detector 900 comprises a first cross-correlationcalculator 904 coupled to a delay element 908. The firstcross-correlation calculator 904 is configured to compute across-correlation between a received signal and the Golay code Ga. Anoutput of the delay element 908 corresponds to a cross-correlationbetween a first occurring symbol and a second occurring symbol the WURpreamble portion 400 and Ga.

The WUR preamble detector 800 also comprises a second cross-correlationcalculator 912. The second cross-correlation calculator 912 isconfigured to compute a cross-correlation between the received signaland the Golay code Gb. An output of the second cross-correlationcalculator 912 corresponds to a cross-correlation between a thirdoccurring symbol and a fourth occurring symbol in the WUR preambleportion 400 and Gb.

The WUR preamble detector 900 also comprises an adder 916, which iscoupled to the output of the delay element 908, and the output of thesecond cross-correlation calculator 912. An output of the adder 916 iscoupled to a buffer 918. In an embodiment, the buffer 918 is configuredto store at least K outputs of the adder 916. When the received signalincludes the WUR preamble portion 400 Ga Ga Gb Gb, the output of theadder 916 will a first sample equal to approximately 2*K, K−1 secondsamples of zeros (or near zero), and then a third sample equal toapproximately 2*K.

The WUR preamble detector 900 also comprises logic 920, which is coupledto the output of the buffer 918. In an embodiment, the logic 920 isconfigured to detect when the output of the adder 916 includes the firstsample equal to approximately 2*K, K−1 second samples of zeros (or nearzero), and then the third sample equal to approximately 2*K. Inresponse, the logic 920 generates a carrier sense (CS) signal toindicate that the preamble (Ga Ga Gb Gb) has been detected.Additionally, the logic 920 uses the first sample equal to approximately2*K, K−1 second samples of zeros (or near zero), and then the thirdsample equal to approximately 2*K to generate a symbol timing (ST)signal that indicates the centers of symbols in the preamble, accordingto an embodiment.

In an embodiment, the logic 920 comprises hardware circuitry (e.g., oneor more comparator circuits, one or more state machine circuits, etc.)configured to implement the functions described above. In anotherembodiment, the logic 920 is implemented using a processor executingmachine readable instructions stored in a memory device, wherein themachined readable instructions, when executed by the processor, causethe processor to implement the functions described above. In anotherembodiment, the logic 920 comprises a combination of i) hardwarecircuitry (e.g., one or more comparator circuits, one or more statemachine circuits, etc.) and ii) a processor executing machined readableinstructions, that together implement the functions described above.

As discussed above, different WUR sync portions and/or different syncsymbols are utilized to indicate different PHY modes of a wakeup packet,at least in some embodiments. Thus, in some embodiments, the LP-WUR 150includes multiple WUR preamble detectors to detect different WUR syncportions corresponding to the different PHY modes. For example, whichone of the multiple WUR preamble detectors detects a WUR preambleindicates a PHY mode of the wakeup packet, according to an embodiment.

In other embodiments, the WUR preamble detector includes differentcross-correlators corresponding to different sync symbols, and the WURpreamble detector uses the different cross-correlators to detect WURsync portions using techniques such as described above. For example,which one of the cross-correlators detects a sync symbol in a WURpreamble indicates a PHY mode of the wakeup packet, according to anembodiment.

FIG. 10 is a flow diagram of an example method 1000 for processingwakeup packets, according to an embodiment. In some embodiments, theLP-WUR 150 of FIGS. 1A and 1D is configured to implement the method1000. The method 1000 is described in the context of the LP-WUR 150merely for explanatory purposes and, in other embodiments, the method1000 is implemented by another network interface device.

At block 1004, the LP-WUR 150 calculates (e.g., the digital basebandcircuitry 188 calculates) one or more correlations on a received signal.The one or more correlations correspond to one or more sync symbolsincluded in a sync portion of a wakeup packet. The wakeup packetincludes i) a first portion having a WLAN legacy preamble that spans afirst frequency bandwidth, and ii) a second portion that follows in timethe first portion and that spans a second bandwidth narrower than thefirst bandwidth. The second portion includes i) the sync portion havinga plurality of sync symbols, and ii) a wakeup packet body.

At block 1008, the LP-WUR 150 detects (e.g., the digital basebandcircuitry 188 detects) the sync portion of the wakeup packet using theone or more correlations.

At block 1012, the LP-WUR 150 determines (e.g., the digital basebandcircuitry 188 determines) a symbol timing using the one or morecorrelations.

At block 1016, the LP-WUR 150 processes (e.g., the digital basebandcircuitry 188 processes) the wakeup packet body based on the determinedsymbol timing.

In some embodiments, the sync portion is modulated according to OOK;each sync symbol is selected from a set consisting of i) a non-zeroenergy sequence, and ii) a zero energy sequence; calculating the one ormore correlations comprises: generating, at the WUR, one or morerespective autocorrelations between expected adjacent sync symbolscorresponding to the non-zero energy sequence, and measuring, at theWUR, one or more energy levels of expected sync symbols corresponding tothe zero energy sequence; detecting the WUR preamble comprises using theone or more respective generated autocorrelations and the one or moremeasured energy levels; and determining the symbol timing comprisesusing the one or more respective generated autocorrelations.

In an embodiment, determining the symbol timing further comprises usingthe one or more measured energy levels.

In some embodiment, the sync portion is modulated according to on-offkeying (OOK); each sync symbol is selected from a set consisting of i) anon-zero energy sequence, ii) the non-zero energy sequence phase rotatedby 180 degrees, and iii) a zero energy sequence; the method furthercomprises: generating, at the WUR, one or more respective correlationsat expected sync symbols corresponding to the non-zero energy sequenceand the non-zero energy sequence phase rotated by 180 degrees, andmeasuring, at the WUR, one or more energy levels at expected syncsymbols corresponding to the zero energy sequence; detecting the WURpreamble comprises using the one or more respective generatedcorrelations and the one or more measured energy levels; and determiningthe symbol timing comprises using the one or more respective generatedautocorrelations.

In an embodiment, determining the symbol timing further comprises usingthe one or more measured energy levels.

In some embodiments, the sync portion is modulated according to aManchester code; each sync symbol is selected from a set consisting ofi) a first sync symbol comprising a) a first occurring non-zero energyportion, and b) a second occurring zero energy portion; and ii) a secondsync symbol comprising a) a first occurring zero energy portion, and b)a second occurring non-zero energy portion;

the method further comprises: generating, at the WUR, one or morerespective correlations at expected non-zero energy portions, andmeasuring, at the WUR, one or more energy levels at expected zero energyportions; detecting the WUR preamble comprises using the one or morerespective generated correlations and the one or more measured energylevels; and determining the symbol timing comprises using the one ormore respective generated autocorrelations.

In an embodiment, determining the symbol timing further comprises usingthe one or more measured energy levels.

In some embodiments, each sync symbol is selected from a set consistingof i) a non-zero energy sequence, and ii) the non-zero energy sequencephase rotated by 180 degrees; the method further comprises: generating,at the WUR, one or more respective correlations regarding the WURpreamble; detecting the WUR preamble comprises using the one or morerespective generated correlations; and determining the symbol timingcomprises using the one or more respective generated autocorrelations.

In some embodiments, each sync symbol comprises one or more Golay codes;the method further comprises: generating, at the WUR, one or morerespective correlations regarding the WUR preamble; detecting the WURpreamble comprises using the one or more respective generatedcorrelations; and determining the symbol timing comprises using the oneor more respective generated autocorrelations.

In some embodiments, the method further comprises: determining, at theWUR, a matching sync portion from a set of candidate sync portions thatis included in the WUR preamble; and determining, at the WUR, a physicallayer (PHY) mode according to which the wakeup packet body wastransmitted based on the determined matching sync portion; whereinprocessing the wakeup packet body is performed in accordance with thedetermined PHY mode.

In some embodiments, the method further comprises: determining, at theWUR, a matching sync symbol from a set of candidate sync symbols that isincluded in the WUR preamble; and determining, at the WUR, a physicallayer (PHY) mode according to which the wakeup packet body wastransmitted based on the determined matching sync symbol; whereinprocessing the wakeup packet body is performed in accordance with thedetermined PHY mode.

Embodiment 1

A method, performed by a first communication device, for transmitting awakeup packet configured to cause a wakeup radio of a secondcommunication device to cause a wireless local area network (WLAN)network interface device of the second communication device totransition from a low power state to an active state, the methodcomprising: generating, at the first communication device, a firstportion of the wakeup packet, wherein the first portion of the wakeuppacket corresponds to a WLAN legacy preamble of the wakeup packet, andwherein the first portion spans a first frequency bandwidth; generating,at the first communication device, a second portion of the wakeuppacket, wherein the second portion of the wakeup packet spans a secondbandwidth that is less than the first bandwidth, and wherein: the secondportion of the wakeup packet is configured to cause the wakeup radio ofthe second communication device to cause the WLAN network interfacedevice of the second communication device to transition from the lowpower state to the active state, generating the second portion of thewakeup packet includes i) generating a sync portion having a pluralityof sync symbols, and ii) generating a wakeup packet body; andtransmitting, by the first communication device, the wakeup packet.

Embodiment 2

The method of Embodiment 1, wherein generating the sync portioncomprises: modulating the sync portion according to on-off keying (OOK);and selecting each sync symbol from a set consisting of i) a non-zeroenergy sequence, and ii) a zero energy sequence.

Embodiment 3

The method of Embodiment 1, wherein generating the sync portioncomprises: modulating the sync portion according to on-off keying (OOK);and selecting each sync symbol from a set consisting of i) a non-zeroenergy sequence, ii) the non-zero energy sequence phase rotated by 180degrees, and iii) a zero energy sequence.

Embodiment 4

The method of Embodiment 1, wherein generating the sync portioncomprises: modulating the sync portion according to a Manchester code;and selecting each sync symbol from a set consisting of i) a first syncsymbol comprising a) a first occurring non-zero energy portion, and b) asecond occurring zero energy portion; and ii) a second sync symbolcomprising a) a first occurring zero energy portion, and b) a secondoccurring non-zero energy portion.

Embodiment 5

The method of Embodiment 1, wherein generating the sync portioncomprises: selecting each sync symbol from a set consisting of i) anon-zero energy sequence, and ii) the non-zero energy sequence phaserotated by 180 degrees.

Embodiment 6

The method of Embodiment 1, wherein: each sync symbol comprises one ormore Golay codes.

Embodiment 7

The method of any of Embodiments 1-6, further comprising: determining,at the first communication device, a physical layer (PHY) mode accordingto which the wakeup packet body is to be transmitted; and selecting, atthe first communication device, the sync portion from a set of candidatesync portions according to the selected PHY mode, wherein the selectedsync portion indicates the PHY mode.

Embodiment 8

The method of any of Embodiments 1-6, further comprising: determining,at the first communication device, a PHY mode according to which thewakeup packet body is to be transmitted; and selecting, at the firstcommunication device, a sync symbol to use for the sync portion from aset of candidate sync symbols according to the selected PHY mode,wherein the selected sync symbol indicates the PHY mode.

Embodiment 9

An apparatus, comprising: a network interface device associated with afirst communication device, wherein the network interface devicecomprises one or more integrated circuit (IC) devices configured to:generate a wireless local area network (WLAN) legacy preamble of awakeup packet, wherein the wakeup packet is configured to cause a wakeupradio of a second communication device to cause a WLAN network interfacedevice of the second communication device to transition from a low powerstate to an active state, generate a first portion of a wakeup packet,wherein the first portion of the wakeup packet corresponds to a wirelesslocal area network (WLAN) legacy preamble of the wakeup packet, andwherein the first portion spans a first frequency bandwidth, generate asecond portion of the wakeup packet, wherein the second portion of thewakeup packet spans a second bandwidth that is less than the firstbandwidth, and wherein: the second portion of the wakeup packet isconfigured to cause a wakeup radio of a second communication device tocause a WLAN network interface device of the second communication deviceto transition from a low power state to an active state, and generatingthe second portion of the wakeup packet includes i) generating a syncportion having a plurality of sync symbols, and ii) generating a wakeuppacket body; wherein the one or more IC devices are further configuredto transmit the wakeup packet.

Embodiment 10

The apparatus of Embodiment 9, wherein the one or more IC devices arefurther configured to: modulate the sync portion according to on-offkeying (OOK); and select each sync symbol from a set consisting of i) anon-zero energy sequence, and ii) a zero energy sequence.

Embodiment 11

The apparatus of Embodiment 9, wherein the one or more IC devices arefurther configured to: modulate the sync portion according to on-offkeying (OOK); and select each sync symbol from a set consisting of i) anon-zero energy sequence, ii) the non-zero energy sequence phase rotatedby 180 degrees, and iii) a zero energy sequence.

Embodiment 12

The apparatus of Embodiment 9, wherein the one or more IC devices arefurther configured to: modulate the sync portion according to aManchester code; and select each sync symbol from a set consisting of i)a first sync symbol comprising a) a first occurring non-zero energyportion, and b) a second occurring zero energy portion; and ii) a secondsync symbol comprising a) a first occurring zero energy portion, and b)a second occurring non-zero energy portion.

Embodiment 13

The apparatus of Embodiment 9, wherein the one or more IC devices arefurther configured to: select each sync symbol from a set consisting ofi) a non-zero energy sequence, and ii) the non-zero energy sequencephase rotated by 180 degrees.

Embodiment 14

The apparatus of Embodiment 9, wherein: each sync symbol comprises oneor more Golay codes.

Embodiment 15

The apparatus of any of Embodiments 9-14, wherein the one or more ICdevices are further configured to: determine a physical layer (PHY) modeaccording to which the wakeup packet body is to be transmitted; andselect the sync portion from a set of candidate sync portions accordingto the selected PHY mode, wherein the selected sync portion indicatesthe PHY mode.

Embodiment 16

The apparatus of any of Embodiments 9-14, wherein the one or more ICdevices are further configured to: determine a PHY mode according towhich the wakeup packet body is to be transmitted; and select a syncsymbol to use for the sync portion from a set of candidate sync symbolsaccording to the selected PHY mode, wherein the selected sync symbolindicates the PHY mode.

Embodiment 17

A method, performed by a wakeup radio (WUR) of a communication device,for processing a wakeup packet configured to cause the WUR of thecommunication device to cause a wireless local area network (WLAN)network interface device of the communication device to transition froma low power state to an active state, wherein the wakeup packet includesi) a first portion having a WLAN legacy preamble that spans a firstfrequency bandwidth, and ii) a second portion that follows in time thefirst portion and that spans a second bandwidth narrower than the firstbandwidth, and wherein the second portion includes i) a sync portionhaving a plurality of sync symbols, and ii) a wakeup packet body, themethod comprising: calculating, at the WUR, one or more correlationscorresponding to one or more sync symbols included in the sync portion;detecting, at the WUR, the sync portion of the wakeup packet using theone or more correlations; determining, at the WUR, a symbol timing usingthe one or more correlations; and processing, at the WUR, the wakeuppacket body based on the determined symbol timing.

Embodiment 18

The method of Embodiment 17, wherein: the sync portion is modulatedaccording to on-off keying (OOK); each sync symbol is selected from aset consisting of i) a non-zero energy sequence, and ii) a zero energysequence; calculating the one or more correlations comprises:generating, at the WUR, one or more respective autocorrelations betweenexpected adjacent sync symbols corresponding to the non-zero energysequence, and measuring, at the WUR, one or more energy levels ofexpected sync symbols corresponding to the zero energy sequence;detecting the sync portion comprises using the one or more respectivegenerated autocorrelations and the one or more measured energy levels;and determining the symbol timing comprises using the one or morerespective generated autocorrelations.

Embodiment 19

The method of Embodiment 18, wherein: determining the symbol timingfurther comprises using the one or more measured energy levels.

Embodiment 20

The method of Embodiment 17, wherein: the sync portion is modulatedaccording to on-off keying (OOK); each sync symbol is selected from aset consisting of i) a non-zero energy sequence, ii) the non-zero energysequence phase rotated by 180 degrees, and iii) a zero energy sequence;the method further comprises: generating, at the WUR, one or morerespective correlations at expected sync symbols corresponding to thenon-zero energy sequence and the non-zero energy sequence phase rotatedby 180 degrees, and measuring, at the WUR, one or more energy levels atexpected sync symbols corresponding to the zero energy sequence;detecting the sync portion comprises using the one or more respectivegenerated correlations and the one or more measured energy levels; anddetermining the symbol timing comprises using the one or more respectivegenerated autocorrelations.

Embodiment 21

The method of Embodiment 20, wherein: determining the symbol timingfurther comprises using the one or more measured energy levels.

Embodiment 22

The method of Embodiment 17, wherein: the sync portion is modulatedaccording to a Manchester code; each sync symbol is selected from a setconsisting of i) a first sync symbol comprising a) a first occurringnon-zero energy portion, and b) a second occurring zero energy portion;and ii) a second sync symbol comprising a) a first occurring zero energyportion, and b) a second occurring non-zero energy portion; the methodfurther comprises: generating, at the WUR, one or more respectivecorrelations at expected non-zero energy portions, and measuring, at theWUR, one or more energy levels at expected zero energy portions;detecting the sync portion comprises using the one or more respectivegenerated correlations and the one or more measured energy levels; anddetermining the symbol timing comprises using the one or more respectivegenerated autocorrelations.

Embodiment 23

The method of Embodiment 22, wherein: determining the symbol timingfurther comprises using the one or more measured energy levels.

Embodiment 24

The method of Embodiment 17, wherein: each sync symbol is selected froma set consisting of i) a non-zero energy sequence, and ii) the non-zeroenergy sequence phase rotated by 180 degrees; the method furthercomprises: generating, at the WUR, one or more respective correlationsregarding the sync portion; detecting the sync portion comprises usingthe one or more respective generated correlations; and determining thesymbol timing comprises using the one or more respective generatedautocorrelations.

Embodiment 25

The method of Embodiment 17, wherein: each sync symbol comprises one ormore Golay codes; the method further comprises: generating, at the WUR,one or more respective correlations regarding the sync portion;detecting the sync portion comprises using the one or more respectivegenerated correlations; and determining the symbol timing comprisesusing the one or more respective generated autocorrelations.

Embodiment 26

The method of any of Embodiments 17-25, further comprising: determining,at the WUR, a matching sync portion from a set of candidate syncportions that is included in the sync portion; and determining, at theWUR, a physical layer (PHY) mode according to which the wakeup packetbody was transmitted based on the determined matching sync portion;wherein processing the wakeup packet body is performed in accordancewith the determined PHY mode.

Embodiment 27

The method of any of Embodiments 17-25, further comprising: determining,at the WUR, a matching sync symbol from a set of candidate sync symbolsthat is included in the sync portion; and determining, at the WUR, aphysical layer (PHY) mode according to which the wakeup packet body wastransmitted based on the determined matching sync symbol; whereinprocessing the wakeup packet body is performed in accordance with thedetermined PHY mode.

Embodiment 28

An apparatus, comprising: a wakeup radio WUR associated with a wirelesslocal area network (WLAN) network interface device, wherein the WURcomprises one or more integrated circuit (IC) devices configured to:process a wakeup packet, wherein the wakeup packet includes i) a firstportion having a WLAN legacy preamble that spans a first frequencybandwidth, and ii) a second portion that follows in time the firstportion and that spans a second bandwidth narrower than the firstbandwidth, and wherein the second portion includes i) the sync portionhaving a plurality of sync symbols, and ii) a wakeup packet body.Processing the wakeup packet includes: calculating one or morecorrelations corresponding to one or more sync symbols included in thesync portion, detecting the sync portion of the wakeup packet using theone or more correlations, determining a symbol timing using the one ormore correlations, and processing the wakeup packet body based on thedetermined symbol timing.

Embodiment 29

The apparatus of Embodiment 28, wherein: the sync portion is modulatedaccording to on-off keying (OOK); each sync symbol is selected from aset consisting of i) a non-zero energy sequence, and ii) a zero energysequence; the one or more IC devices are configured to: generate one ormore respective autocorrelations between expected adjacent sync symbolscorresponding to the non-zero energy sequence, and measure one or moreenergy levels of expected sync symbols corresponding to the zero energysequence, detect the sync portion using the one or more respectivegenerated autocorrelations and the one or more measured energy levels,and determine the symbol timing using the one or more respectivegenerated autocorrelations.

Embodiment 30

The apparatus of Embodiment 29, wherein the one or more IC devices areconfigured to: determine the symbol timing using the one or moremeasured energy levels.

Embodiment 31

The apparatus of Embodiment 28, wherein: the sync portion is modulatedaccording to on-off keying (OOK); each sync symbol is selected from aset consisting of i) a non-zero energy sequence, ii) the non-zero energysequence phase rotated by 180 degrees, and iii) a zero energy sequence;the one or more IC devices are configured to: generate one or morerespective correlations at expected sync symbols corresponding to thenon-zero energy sequence and the non-zero energy sequence phase rotatedby 180 degrees, measure one or more energy levels at expected syncsymbols corresponding to the zero energy sequence, detect the syncportion using the one or more respective generated correlations and theone or more measured energy levels, and determine the symbol timingusing the one or more respective generated autocorrelations.

Embodiment 32

The apparatus of Embodiment 31, wherein the one or more IC devices areconfigured to: determine the symbol timing using the one or moremeasured energy levels.

Embodiment 33

The apparatus of Embodiment 28, wherein: the sync portion is modulatedaccording to a Manchester code; each sync symbol is selected from a setconsisting of i) a first sync symbol comprising a) a first occurringnon-zero energy portion, and b) a second occurring zero energy portion;and ii) a second sync symbol comprising a) a first occurring zero energyportion, and b) a second occurring non-zero energy portion; the one ormore IC devices are configured to: generate one or more respectivecorrelations at expected non-zero energy portions, measure one or moreenergy levels at expected zero energy portions, detect the sync portionusing the one or more respective generated correlations and the one ormore measured energy levels, and determine the symbol timing using theone or more respective generated autocorrelations.

Embodiment 34

The apparatus of Embodiment 33, wherein the one or more IC devices areconfigured to: determine the symbol timing using the one or moremeasured energy levels.

Embodiment 35

The apparatus of Embodiment 28, wherein: each sync symbol is selectedfrom a set consisting of i) a non-zero energy sequence, and ii) thenon-zero energy sequence phase rotated by 180 degrees; the one or moreIC devices are configured to: generate one or more respectivecorrelations regarding the sync portion, detect the sync portion usingthe one or more respective generated correlations, and determine thesymbol timing using the one or more respective generatedautocorrelations.

Embodiment 36

The apparatus of Embodiment 28, wherein: each sync symbol comprises oneor more Golay codes; the one or more IC devices are configured to:generate one or more respective correlations regarding the sync portion,detect the sync portion comprises using the one or more respectivegenerated correlations, and determine the symbol timing using the one ormore respective generated autocorrelations.

Embodiment 37

The apparatus of any of Embodiments 28-36, wherein the one or more ICdevices are configured to: determine a matching sync portion from a setof candidate sync portions that is included in the second portion of thewakeup packet; determine a physical layer (PHY) mode according to whichthe wakeup packet body was transmitted based on the determined matchingsync portion; and process the wakeup packet body in accordance with thedetermined PHY mode.

Embodiment 38

The apparatus of any of Embodiments 28-36, wherein the one or more ICdevices are configured to: determine a matching sync symbol from a setof candidate sync symbols that is included in the second portion of thewakeup packet; determine a physical layer (PHY) mode according to whichthe wakeup packet body was transmitted based on the determined matchingsync symbol; and process the wakeup packet body in accordance with thedetermined PHY mode.

At least some of the various blocks, operations, and techniquesdescribed above may be implemented utilizing hardware, a processorexecuting firmware instructions, a processor executing softwareinstructions, or any combination thereof. When implemented utilizing aprocessor executing software or firmware instructions, the software orfirmware instructions may be stored in any computer readable memory suchas on a magnetic disk, an optical disk, or other storage medium, in aRAM or ROM or flash memory, processor, hard disk drive, optical diskdrive, tape drive, etc. The software or firmware instructions mayinclude machine readable instructions that, when executed by one or moreprocessors, cause the one or more processors to perform various acts.

When implemented in hardware, the hardware may comprise one or more ofdiscrete components, an integrated circuit, an application-specificintegrated circuit (ASIC), a programmable logic device (PLD), etc.

While the present invention has been described with reference tospecific examples, which are intended to be illustrative only and not tobe limiting of the invention, changes, additions and/or deletions may bemade to the disclosed embodiments without departing from the scope ofthe invention.

What is claimed is:
 1. A method, performed by a first communicationdevice, for transmitting a wakeup packet, the method comprising:determining, at a first communication device, a data rate for a wakeuppacket body of the wakeup packet; selecting, at the first communicationdevice, a sync portion for the wakeup packet from a set of multiplecandidate sync portions based on the determined data rate, wherein themultiple candidate sync portions in the set are configured to indicaterespective data rates, and wherein each candidate sync portion comprisesa respective plurality of on-off keying-modulated (OOK-modulated) syncsymbols; generating, at the first communication device, a first portionof the wakeup packet, wherein the first portion of the wakeup packetcorresponds to a wireless local area network (WLAN) legacy preamble ofthe wakeup packet, and wherein the first portion spans a first frequencybandwidth; generating, at the first communication device, a secondportion of the wakeup packet, wherein the second portion of the wakeuppacket spans a second bandwidth that is less than the first bandwidth,and wherein: generating the second portion of the wakeup packet includesi) generating the selected sync portion to indicate to the secondcommunication device the determined data rate of the wakeup packet body,and ii) generating the wakeup packet body according to the determineddata rate, wherein generating the selected sync portion includesselecting each sync symbol in the selected sync portion from a setincluding a) a non-zero energy sequence and b) a zero energy sequence toenable the second communication device to: detect the sync portion basedon i) one or more respective autocorrelations, generated at the secondcommunication device, between expected adjacent sync symbolscorresponding to the non-zero energy sequence and ii) one or more energylevels, measured at the second communication device, of expected syncsymbols corresponding to the zero energy sequence, and determine asymbol timing using the one or more respective autocorrelations; andtransmitting, by the first communication device, the wakeup packet. 2.The method of claim 1, wherein generating the sync portion comprises:selecting each sync symbol in the selected sync portion from the setfurther including the non-zero energy sequence phase rotated by 180degrees.
 3. An apparatus, comprising: a network interface deviceassociated with a first communication device, wherein the networkinterface device comprises one or more integrated circuit (IC) devicesconfigured to: determine a data rate for a wakeup packet body of awakeup packet, select a sync portion for the wakeup packet from a set ofmultiple candidate sync portions based on the determined data rate,wherein the multiple candidate sync portions in the set are configuredto indicate respective data rates, and wherein each candidate syncportion comprises a respective plurality of on-off keying-modulated(OOK-modulated) sync symbols; generate a first portion of the wakeuppacket, wherein the first portion of the wakeup packet corresponds to awireless local area network (WLAN) legacy preamble of the wakeup packet,and wherein the first portion spans a first frequency bandwidth,generate a second portion of the wakeup packet, wherein the secondportion of the wakeup packet spans a second bandwidth that is less thanthe first bandwidth, and wherein: generating the second portion of thewakeup packet includes i) generating the selected sync portion toindicate to a second communication device the determined data rate ofthe wakeup packet body, and ii) generating the wakeup packet bodyaccording to the determined data rate, wherein generating the selectedsync portion includes selecting each sync symbol in the selected syncportion from a set including a) a non-zero energy sequence and b) a zeroenergy sequence to enable the second communication device to: detect thesync portion based on i) one or more respective autocorrelations,generated at the second communication device, between expected adjacentsync symbols corresponding to the non-zero energy sequence and ii) oneor more energy levels, measured at the second communication device, ofexpected sync symbols corresponding to the zero energy sequence, anddetermine a symbol timing using the one or more respectiveautocorrelations; wherein the one or more IC devices are furtherconfigured to transmit the wakeup packet.
 4. The apparatus of claim 3,wherein the one or more IC devices are further configured to: selecteach sync symbol in the selected sync portion from the set furtherincluding the non-zero energy sequence phase rotated by 180 degrees. 5.A method, performed by a wakeup radio (WUR) of a communication device,for processing a wakeup packet, wherein the wakeup packet includes i) afirst portion having a wireless local area network (WLAN) legacypreamble that spans a first frequency bandwidth, and ii) a secondportion that follows in time the first portion and that spans a secondbandwidth narrower than the first bandwidth, and wherein the secondportion includes i) a sync portion having a plurality of sync symbols,and ii) a wakeup packet body, the method comprising: calculating, at theWUR, one or more correlations corresponding to one or more sync symbolsincluded in the sync portion, wherein the sync portion is modulatedaccording to on-off keying (OOK), wherein each sync symbol is selectedfrom a set consisting of a) a non-zero energy sequence, and b) a zeroenergy sequence, and wherein calculating the one or more correlationscomprises: generating, at the WUR, one or more respectiveautocorrelations between expected adjacent sync symbols corresponding tothe non-zero energy sequence, and measuring, at the WUR, one or moreenergy levels of expected sync symbols corresponding to the zero energysequence; detecting, at the WUR, the sync portion of the wakeup packetusing the one or more respective generated autocorrelations and the oneor more measured energy levels; determining, at the WUR, that thedetected sync portion corresponds to a matching sync portion from a setof candidate sync portions that respectively correspond to differentdata rates of the wakeup packet body; determining, at the WUR, a datarate according to which the wakeup packet body was transmitted based onthe determined matching sync portion; determining, at the WUR, a symboltiming using the one or more respective generated autocorrelations; andprocessing, at the WUR, the wakeup packet body based on the determinedsymbol timing and in accordance with the determined data rate.
 6. Themethod of claim 5, wherein: determining the symbol timing furthercomprises using the one or more measured energy levels.
 7. The method ofclaim 5, wherein: each sync symbol is selected from set furtherincluding the non-zero energy sequence phase rotated by 180 degrees. 8.The method of claim 7, wherein: determining the symbol timing furthercomprises using the one or more measured energy levels.
 9. An apparatus,comprising: a wakeup radio WUR associated with a wireless local areanetwork (WLAN) network interface device, wherein the WUR comprises oneor more integrated circuit (IC) devices configured to: process a wakeuppacket, wherein the wakeup packet includes i) a first portion having aWLAN legacy preamble that spans a first frequency bandwidth, and ii) asecond portion that follows in time the first portion and that spans asecond bandwidth narrower than the first bandwidth, and wherein thesecond portion includes i) a sync portion having a plurality of syncsymbols and being modulated according to on-off keying (OOK), and ii) awakeup packet body, wherein processing the wakeup packet includes:calculating one or more correlations corresponding to one or more syncsymbols included in the sync portion, wherein each sync symbol isselected from a set consisting of i) a non-zero energy sequence, and ii)a zero energy sequence, and wherein calculating the one or morecorrelations comprises: generating, at the WUR, one or more respectiveautocorrelations between expected adjacent sync symbols corresponding tothe non-zero energy sequence, and measuring, at the WUR, one or moreenergy levels of expected sync symbols corresponding to the zero energysequence, detecting the sync portion of the wakeup packet using the oneor more respective generated autocorrelations and the one or moremeasured energy levels, determining that the detected sync portioncorresponds to a matching sync portion from a set of candidate syncportions that respectively correspond to different data rates of thewakeup packet body, determining a data rate according to which thewakeup packet body was transmitted based on the determined matching syncportion, determining a symbol timing using the one or more respectivegenerated autocorrelations, and processing the wakeup packet body basedon the determined symbol timing and in accordance with the determineddata rate.
 10. The apparatus of claim 9, wherein the one or more ICdevices are configured to: determine the symbol timing using the one ormore measured energy levels.
 11. The apparatus of claim 9, wherein: eachsync symbol is selected from the set further including the non-zeroenergy sequence phase rotated by 180 degrees.
 12. The apparatus of claim11, wherein the one or more IC devices are configured to: determine thesymbol timing using the one or more measured energy levels.